Linear Actuator

ABSTRACT

A linear actuator has an alternating drive apparatus, an alternating motion member, a fixing member fixed to a housing member, a direct acting member, a first wedge joining mechanism incorporated between the alternating motion member and the direct acting member, and a second wedge joining mechanism incorporated between the fixing member and the direct acting member. The first wedge joining mechanism and the second wedge joining mechanism have an inclined surface, a non-inclined surface at a constant distance from the central axis, and a wedge member arranged between the inclined surface and the non-inclined surface. The non-inclined surfaces of the first and second wedge joining mechanisms are formed on the direct acting member. The inclined surface of the first wedge joining mechanism is formed on the alternating motion member, and the inclined surface of the second wedge joining mechanism is formed to the fixing member.

CLAIM OF PRIORITY

This application is a divisional of U.S. patent application Ser. No.11/958,681, filed Dec. 18, 2007, the entire disclosure of which isexpressly incorporated herein by reference, and claims priority fromboth Japanese Application Ser. No. 2006-341349, filed on Dec. 19, 2006,and Japanese Application Ser. No. 2007-066943, filed on Mar. 15, 2007,the contents of which are also incorporated by reference into thisapplication.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a linear actuator utilized as a drivesource of various devices including a car and more particularly to alinear actuator for accumulating one-way motion from an alternatingmotion with a micro amplitude by an alternating drive source forgenerating drive force back and forth in the axial direction, therebycreating a direct motion.

2. Prior Art

Devices such as an automatic transmission (automatic MT) for driving ashift lever for switching the combination of the shift gears for a carby a motor instead of a hand and a variable operating valve device forcontrolling optimally the lift amount of the valve of an engine or theopening period thereof according to the operation state realize thecompatibility of improvement of the comfortableness of a car withimprovement of fuel expenses, thus future enlargement of use isexpected. Unlike other more general machines driven directly by arotation actuator such as a motor for repeating continuously apredetermined operation, the concerned devices are controlled directlyat optimum positions according to the circumstances and instead of therotation actuator, are driven by a linear actuator for outputting adirect motion.

Therefore, in the devices such as the automatic transmission andvariable operating valve device, the performance of the linear actuatorcontrols the performance of the overall devices. For example, if thereis a linear actuator for responding at a high speed available, a deviceusing it can function at a high speed and if there is a compact linearactuator with high thrust available, an overall device incorporating itcan be made compact. To minimize the control delay for a control subjectsuch as the transmission gear ratio or valve operation for suddenchanges in the operation conditions of a car such as the car speed andengine load changing every moment and maintain always the car in anoptimum state, particularly the characteristic of the high speedresponse aforementioned is important.

As a linear actuator, conventionally, an article structured so as tocreate a direct motion by a ball screw and a worm gear from the rotarymotion of the motor has been used, though to generate large thrust ofthe direct motion with limited motor torque, a concept is used that themotor is rotated at a high speed to ensure the output, and it isdecelerated at the stage of realization of direct motion, thus largethrust is generated. Therefore, to speed up the direct motion, it isessential to speed up the rotation of the motor. On the other hand, thespeedup of the linear actuator is evaluated by the shortness of the timerequired to move by a predetermined stroke from the standstill. Thisindicates that in a conventional linear actuator driven by a motor, therotation system must be put into a high-speed rotation state in a shorttime, so that the output of the motor is consumed to increase thekinetic energy of the rotation system. In other words, it may be saidthat at start time of the linear actuator, a large inertia resistance isacted. In the linear actuator of the conventional type, the inertiaresistance may be considered to be an obstacle to speedup.

As a means for avoiding the obstacle to speedup, a linear actuator foraccumulating one-way motion from an alternating motion with a microamplitude by an alternating drive source for generating drive force backand forth in the axial direction of a magnetostrictor, thereby creatinga direct motion is known. Generally, the alternating drive sourceobtains only a micro amplitude, though can generate large thrust, sothat there is no need to permit the magnetostrictor to move back andforth at a high speed, then decelerate, thereby enlarge the thrust, thusit can be expected that the inertia resistance will be reduced.

As a prior art of the linear actuator by the alternating drive sourceusing the magnetostrictor, for example, as described in Patent Document1, a linear actuator for acting a fluid pressure on a piston using acheck valve, thereby generating a direct motion is proposed. It isdisclosed as a one that a hydraulic chamber is formed at the end of themember for moving back and forth with a micro amplitude by themagnetostrictor, and a fluid is pumped in one direction by two checkvalves functioning as an inlet valve and a discharge valve, and thefluid pressure is acted on the piston, thus direct drive force isgenerated.

Further, as another prior art, as described in Patent Document 2, alinear actuator for generating a direct motion using a wedge mechanismfor permitting only a relative motion in one axial direction isproposed. Also in this case, a linear actuator is disclosed that a firstwedge mechanism having an alternating motion member for moving back andforth with a micro amplitude by the magnetostrictor for permitting onlya relative motion in one axial direction is arranged between thealternating motion member and the output member for executing the directmotion, and furthermore, a second wedge mechanism for permitting only arelative motion in one axial direction is arranged between the outputmember and the fixed frame member, and the one-direction motion of thealternating motion is accumulated by a combination of the wedgemechanisms, thus a direct motion is generated.

-   Patent Document 1: Japanese Patent Application Laid-open Publication    No. Hei 9 (1997)-303451-   Patent Document 2: Japanese Patent Application Laid-open Publication    No. 2005-33978

SUMMARY OF THE INVENTION

However, the prior art disclosed in Patent Document 1 aforementioned isstructured so as to transfer the drive force for the direct motion viathe fluid pressure and there are possibilities that the hydraulic oil inuse externally leaks slowly due to the pressure difference. Therefore,problems of restrictions arise that the maintenance for replenishment isnecessary and the art cannot be used in an environment dislikingcontamination due to leaked oil.

In the prior art disclosed in Patent Document 2 aforementioned, there isno need to enlarge the thrust by deceleration, and by accelerating thedrive source to a high speed at start time, the inertia resistance canbe avoided from increasing, though a problem arises that another factor,indicated below, for increasing the inertia resistance is left. Firstly,as a linear actuator for controlling each device, there is a case that afunction for not only executing the direct motion in one direction butalso switching the direct acting direction (switching one direction orthe reverse direction) is essential, though in the prior art disclosedin Patent Document 2 aforementioned, the mechanical member for theswitching function and the drive apparatus for driving it are structuredso as to be mounted in the output member for executing the direct motionand a problem arises that by adding each mass, the inertia resistance isincreased. Further, the drive apparatus of the mechanism for switchingthe direct acting direction executes the direct motion, so that the leadwire for supplying power to it is deformed repeatedly in correspondencewith the operation of the actuator, so that there is a problem imposedin the durability.

Further, in the prior art disclosed in Patent Document 2 aforementioned,the output member for executing the direct motion is arranged on theouter periphery of the alternating motion member for moving back andforth with a micro amplitude by the alternating drive source, so thatthe diameter is increased, and the mass of the output member itself isincreased, thus a problem arises that the inertia resistance isincreased.

Furthermore, in the prior art disclosed in Patent Document 2aforementioned, there are wedge joining mechanisms installed between theoutput member for executing the direct motion and the alternating motionmember and between the output member and the frame member, and there aretwo systems of wedge joining mechanisms for inhibiting the relativemotion in one axial direction and other axial direction which areinstalled in each of them, and furthermore, in each system, a pluralityof wedge joining mechanisms are arranged in the circumferentialdirection, so that many wedge joining mechanisms, many switchingmechanisms corresponding to them, and drive apparatuses thereof arerequired. In correspondence with it, a problem arises that the number ofcomponents and the processing man-hour of the inclined surfaces of thewedge joining mechanisms are increased, causing an increase in cost.

Further, in the prior art disclosed in Patent Document 2, there is noneed to enlarge the thrust by deceleration and by accelerating the drivesource to a high speed at start time, the inertia resistance can beavoided from increasing. However, only by the wedge joining section fortransferring the drive force of the direct motion, the output shaft issupported in the radial direction. Therefore, problems arise that (1)there are possibilities that a load acting externally on the outputshaft may act on the wedge joining section, thereby may damage it oradversely affect the operation of the generation mechanism of the directmotion, (2) there are possibilities that the inertia force of thealternating motion member may impose a problem of vibration as avibration source, and (3) to avoid interference of the drive section ofthe alternating motion with the output shaft of the direct motion, it isdifficult to realize miniaturization of the apparatus or extension ofthe output stroke.

The object of the present invention is intended to provide a linearactuator enable to accumulate the directional component of thealternating motion by the alternative drive source for creating a directmotion, and realize a high-speed response.

To achieve the above object, the present invention adopts mainly thefollowing constitution.

A linear actuator comprising: an alternating drive apparatus forgenerating drive force back and forth in the axial direction, analternating motion member for executing alternating motion with a microamplitude by the alternating drive apparatus, a fixing member fixed to ahousing member, a direct acting member for executing direct motion backand forth in the axial direction, a first wedge joining mechanismincorporated between the alternating motion member and the direct actingmember for permitting a relative displacement in one axial direction andinhibiting a relative displacement in the other axial direction, and asecond wedge joining mechanism incorporated between the fixing memberand the direct acting member for permitting a relative displacement inone axial direction and inhibiting a relative displacement in the otheraxial direction, wherein: the first wedge joining mechanism and secondwedge joining mechanism include an inclined surface composed of aninclined surface at a distance from the central axis increasing in theaxial direction and an inclined surface at a distance decreasing, anon-inclined surface at a constant distance from the central axis, wedgemembers arranged between the inclined surface and the non-inclinedsurface, holding members of the wedge members for inhibiting wedgejoining by the inclined surface, non-inclined surface, and wedgemembers, and a wedge joint inhibition mechanism composed of the drivesections of the holding members, and the non-inclined surface of thefirst wedge joining mechanism and the non-inclined surface of the secondwedge joining mechanism are installed on the direct acting member, andthe inclined surface of the first wedge joining mechanism is installedon the alternating motion member, and the inclined surface of the secondwedge joining mechanism are fixed to the fixing member.

A linear actuator comprising: first and second joint members, a housingmember for storing the first and second joint members, a drive apparatusfor driving the first and second joint members in a mutually approachingdirection thereof and in a separating direction thereof in the housingmember, a direct acting member joined to the first and second jointmembers for executing a linear motion in an axial direction, a firstwedge joining mechanism incorporated between the first joint member andthe direct acting member for permitting a relative displacement in oneaxial direction between the first joint member and the direct actingmember and inhibiting a relative displacement in the other axialdirection between the first joint member and the direct acting member,and a second wedge joining mechanism incorporated between the secondjoint member and the direct acting member for permitting a relativedisplacement in one axial direction between the second joint member andthe direct acting member and inhibiting a relative displacement in theother axial direction between the second joint member and the directacting member, wherein: the first wedge joining mechanism and the secondwedge joining mechanism include an inclined surface at a distance from acentral axis changing in the axial direction, a non-inclined surface ata constant distance from the central axis, and a wedge member arrangedbetween them, and the direct acting member is supported in a radialdirection by a shaft support section provided in the housing member.

A linear actuator comprising: an alternating drive apparatus forgenerating drive force back and forth in an axial direction, analternating motion member for executing alternating motion with a microamplitude by the alternating drive apparatus, a fixing member fixed to ahousing member, a direct acting member for executing direct motion backand forth in the axial direction, a first wedge joining mechanismincorporated between the alternating motion member and the direct actingmember for permitting a relative displacement in one axial direction andinhibiting a relative displacement in the other axial direction, and asecond wedge joining mechanism incorporated between the fixing memberand the direct acting member for permitting a relative displacement inone axial direction and inhibiting a relative displacement in the otheraxial direction, wherein: the first wedge joining mechanism and thesecond wedge joining mechanism include an inclined surface composed ofan inclined surface at a distance from a central axis increasing in theaxial direction and an inclined surface at a distance decreasing, anon-inclined surface at a constant distance from the central axis, awedge member arranged between the inclined surface and the non-inclinedsurface, a holding member of the wedge member for inhibiting wedgejoining by the inclined surface, the non-inclined surface, and the wedgemember, and a wedge joint inhibition mechanism composed of a drivesection of the holding member, and the non-inclined surface of the firstwedge joining mechanism and the non-inclined surface of the second wedgejoining mechanism are formed on the direct acting member, and theinclined surface, the holding member, and the wedge member arerestricted on a position in a moving direction of the direct actingmember to the housing member and are restricted on a position in aradial direction by the direct acting member.

According to the present invention, a linear actuator enable toaccumulate the directional component of the alternating motion by thealternative drive source for creating a direct motion, and realize ahigh-speed response can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view in the axial direction of the linearactuator relating to the first embodiment of the present invention whenthe output shaft thereof is stopped, which is a sectional view A-A shownin FIGS. 2 to 5.

FIG. 2 is a transverse cross sectional view of the section B-B of thelinear actuator relating to the first embodiment of the presentinvention shown in FIG. 1.

FIG. 3 is a transverse cross sectional view of the section C-C of thelinear actuator relating to the first embodiment of the presentinvention shown in FIG. 1.

FIG. 4 is a transverse cross sectional view of the section D-D of thelinear actuator relating to the first embodiment of the presentinvention shown in FIG. 1.

FIG. 5 is a transverse cross sectional view of the section E-E of thelinear actuator relating to the first embodiment of the presentinvention shown in FIG. 1.

FIG. 6 is a drawing of the wedge joining mechanism of the linearactuator arranged in the circumferential direction shown in FIG. 1 whichis developed on a plane.

FIG. 7 is a cross sectional view in the axial direction of the linearactuator relating to the first embodiment when the output shaft thereofis driven in the right direction in the drawing.

FIG. 8 is a drawing of the wedge joining mechanism of the linearactuator arranged in the circumferential direction shown in FIG. 7 whichis developed on a plane.

FIG. 9 is a cross sectional view in the axial direction of the linearactuator relating to the first embodiment when the output shaft thereofis driven in the left direction in the drawing.

FIG. 10 is a drawing of the wedge joining mechanism of the linearactuator arranged in the circumferential direction shown in FIG. 9 whichis developed on a plane.

FIG. 11 is a cross sectional view in the axial direction of the linearactuator relating to the second embodiment of the present invention whenthe output shaft thereof is driven in the left direction in the drawing.

FIG. 12 is a cross sectional view in the axial direction of the linearactuator relating to the third embodiment of the present invention.

FIG. 13 is a drawing of one of the two wedge joining mechanisms of thelinear actuator arranged in the circumferential direction shown in FIG.12 which is developed on a plane.

FIG. 14 is a drawing of the other one of the two wedge joiningmechanisms of the linear actuator arranged in the circumferentialdirection shown in FIG. 12 which is developed on a plane.

FIG. 15 is a cross sectional view in the axial direction of the linearactuator relating to the fourth embodiment of the present invention.

FIG. 16 is a transverse cross sectional view showing the sections B-Band E-E of the linear actuator relating to the fourth embodiment of thepresent invention shown in FIG. 15.

FIG. 17 is a transverse cross sectional view to show the sections C-Cand D-D of the linear actuator relating to the fourth embodiment of thepresent invention shown in FIG. 15.

FIG. 18 is a drawing to show a principle of driving the output shaftwhen the distance in the axial direction between the joint members isincreased in the linear actuator relating to the fourth embodiment ofthe present invention shown in FIG. 15.

FIG. 19 is a drawing showing the principle of driving the output shaftwhen the distance in the axial direction between the joint members isdecreased in the linear actuator relating to the fourth embodiment ofthe present invention shown in FIG. 15.

FIG. 20 is a cross sectional view in the axial direction of the linearactuator relating to the fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The linear actuators relating to the first, second, third, fourth andfifth embodiments of the present invention will be explained in detailbelow with reference to FIGS. 1 to 20.

First Embodiment

The linear actuator relating to the first embodiment of the presentinvention will be explained by referring to FIGS. 1 to 10. FIG. 1 is across sectional view in the axial direction of the linear actuatorrelating to the first embodiment of the present invention when theoutput shaft thereof is stopped, which is a sectional view A-A shown inFIGS. 2 to 5. FIG. 2 is a transverse cross sectional view of the sectionB-B shown in FIG. 1. FIG. 3 is a transverse cross sectional view of thesection C-C shown in FIG. 1. FIG. 4 is a transverse cross sectional viewof the section D-D shown in FIG. 1. FIG. 5 is a transverse crosssectional view of the section E-E shown in FIG. 1.

FIG. 6 is a drawing of the wedge joining mechanism of the linearactuator arranged in the circumferential direction shown in FIG. 1 whichis developed on a plane. FIG. 7 is a cross sectional view in the axialdirection of the linear actuator relating to the first embodiment whenthe output shaft thereof is driven in the right direction in thedrawing. FIG. 8 is a drawing of the wedge joining mechanism of thelinear actuator arranged in the circumferential direction shown in FIG.7 which is developed on a plane. FIG. 9 is a cross sectional view in theaxial direction of the linear actuator relating to the first embodimentwhen the output shaft thereof is driven in the left direction in thedrawing. FIG. 10 is a drawing of the wedge joining mechanism of thelinear actuator arranged in the circumferential direction shown in FIG.9 which is developed on a plane.

In FIG. 1, an alternating drive apparatus 1 is composed of a fixed ironcore 2, a frame 3, a coil 4, a movable iron core 5, and a plate spring6. To the movable iron core 5, the plate spring 6 and a vibration ring 7which is an alternating motion member are concurrently fixed with a nut8. The outer peripheral part of the plate spring 6 and the housingmember 9 are concurrently fixed to the frame 3 with a peripheral nut 10.To the housing member 9, a fixing ring 11 is fixed.

On each inner peripheral side of a ring 7 a of a vibration ring 7 and aring 11 a of the fixing ring 11, a direct acting rod 12 which is adirect acting member is arranged, and between the direct acting rod 12and the ring 7 a, three rollers (i) 13 are arranged as shown in FIG. 2in the circumferential direction at the positions in the axial directionindicated by the section B-B, and three rollers (ii) 14 are arranged asshown in FIG. 3 in the circumferential direction at the positions in theaxial direction indicated by the section C-C. Further, between thedirect acting rod 12 and the ring 11 a, three rollers (iii) 15 arearranged as shown in FIG. 4 in the circumferential direction at thepositions in the axial direction indicated by the section D-D, and threerollers (iv) 16 are arranged as shown in FIG. 5 in the circumferentialdirection at the positions in the axial direction indicated by thesection E-E.

The rollers 13, 14, 15, and 16 function as a wedge member and as shownin the development elevation in FIG. 6, are arranged in the up and downdirection equivalent to the circumferential direction by the holdingmember 17 and have slight gaps against the respective axial end faces ofthe holding member 17. Each of pressing springs (ii) 18 is arrangedbetween the vibration ring 7 and the roller (ii) 14 and presses theroller (ii) 14 rightward in the axial direction in the drawing. Each ofpressing springs (i-iv) 19 is arranged between the roller (i) 13 and theroller (iv) 16 and presses the rollers in the axial direction inverselyto each other. Each of pressing springs (iii) 20 is arranged between thefixing ring 11 and the roller (iii) 15 and presses the roller (iii)leftward in the drawing in the axial direction.

On each inner peripheral surface of the ring 7 a of the vibration ring 7and the ring 11 a of the fixing ring 11, the spherical surface portion 7b and spherical surface portion 11 b are formed. The contour shape ofthe outside diameter part of each roller is formed at a similarcurvature to the great circle (the circle of the section cut along theplane passing the center of the sphere) of the sphere of the sphericalsurface portion 7 b or 11 b, thus each roller can make almost linecontact with the spherical surface portion 7 b or 11 b (as found fromthe shape of the rollers 13 to 16 shown in FIGS. 1 and 2, each roller isin a shape that both ends of an acorn are cut off or in a shape of adrum having a swelled body center, and the roller is arranged so thatthe central axis passing both cut sections is made parallel with thesheet of paper of FIG. 2, and the shape viewed from the perpendicularsurface of the central axis is the circular shape of the rollers shownin FIG. 1). The direct acting rod 12 has a sectional shape as shown inFIGS. 2 to 5 and on the part thereof with which the outside diameterpart of each roller is in contact, the concave groove 12 a at an almostsimilar curvature to the great circle of the spherical surface isformed. The spherical surface portions 7 b and 11 b are in the same sizeand the rollers are all the same in the contour shape of the outsidediameter part. As a result, the rollers (i) and (iv) can share theconcave groove 12 a with which they are in contact and the rollers (ii)and (iii) can share the concave groove 12 a with which they are incontact.

Each roller is in contact with each spherical surface at the shiftedposition in the axial direction (an output shaft 31) from the sphericalcenter of the spherical surface portion 7 b or lib (on the sheet ofpaper of FIG. 1, the rollers 13 and 14 are shifted left and right) andthe spherical surface portions at the contacting parts are inclined inthe axial direction (in FIG. 1, the spherical surface portion 7 b istapered). The roller (i) 13 and roller (ii) 14 are in contact with thespherical surface portion 7 b at the shifted positions in the reverseaxial directions from the spherical center, so that the inclinationdirections of the spherical surface portions in contact are reverse toeach other. The roller (iii) 15 and roller (iv) 16 are also in contactwith the spherical surface portion lib at the shifted positions in thereverse axial directions from the spherical center, so that theinclination directions of the spherical surface portions in contact arereverse to each other. The direct acting rod 12 has a part formed in afixed transverse cross sectional shape and the concave groove 12 aexisting in the part is a non-inclined surface not inclined in the axialdirection (in FIG. 1, the surfaces of the direct acting rod 12 incontact with the rollers 13 to 16 are not inclined in the axialdirection of the output shaft 31).

The axial position of the holding member 17 shown in FIG. 1 is aposition having a slight gap formed between the axial end faces thereofand all the rollers (in FIG. 6, all the rollers form a slight gapagainst the end face of the holding member 17 in the axial direction ofthe output shaft 31), so that all the rollers are not inhibited from theaxial movement by the holding member 17 and form wedge joints heldbetween the spherical surface portion 7 b or 11 b and the concave groove12 a by each pressing force of the pressing spring (ii) 18, pressingsprings (i-iv) 19, and pressing spring (iii) 20. Here, the sphericalsurface portion 7 b or 11 b is equivalent to an inclined surface forforming a wedge joint, and the rollers (i) 13 to (iv) 16 are equivalentto a wedge member, and the concave groove 12 a is equivalent to anon-inclined surface.

In the neighborhood of the ends of the holding member 17 in the rightdirections shown in FIG. 1, three connection pins 21 are fixed and areprojected on the outer peripheral side from an opening 11 c formed inthe fixing ring 11 and the projected part thereof is fixed to a slidemember (i) 22. Furthermore, in the neighborhood of the end of the slidemember (i) 22 in the right direction, a disk 23 made of a magneticsubstance is fixed. The slide member (i) 22 is pressed in the rightdirection in the drawing by a pressing spring (v) 24. On the left of thedisk 23, a coil (i) 26 stored in a U-shaped magnetic case (i) 25 isfixed and when power is supplied to the coil (i) 26, the disk 23 andmagnetic case (i) 25 form a magnetic circuit and can attract the disk 23in the left direction.

On the right of the slide member (i) 22, a slide member (ii) 27 isarranged and on the right of the disk 23, a coil (ii) 29 stored in aU-shaped magnetic case (ii) 28 is fixed to a nose 11 d of the fixingring 11. The slide member (ii) 27 is pressed leftward in the drawing bya pressing spring (vi) 30 having a larger pressing force than that ofthe pressing spring (v) 24, though it makes contact with the magneticcase (ii) 28 fixed to the nose 11 d, thereby is restricted on leftwardmovement. When power is supplied to the coil (ii) 28, the disk 23 andmagnetic case (ii) 28 form a magnetic circuit and can attract the disk23 in the right direction. At the end of a nose 12 b of the directacting rod 12, the output shaft 31 is fixed with a nut 32.

FIG. 1 shows the state that no power is supplied to both coils (i) 26and (ii) 29. At this time, no magnetic attraction force is acted on thedisk 23 in all the axial directions, so that for the slide members (i)22 and (ii) 27, the axial positions thereof are decided according to therelative strength of the pressing springs. The slide members (i) 22 and(ii) 27 are pressed by the pressing springs (v) 24 and (vi) 30 in thereverse directions and press each other, though the pressing force ofthe pressing spring (vi) 30 is larger than the other, thus both moveleftward as a whole, and the slide member (ii) 27 makes contact with themagnetic case (ii) 28 and stops. The disk 23, at this time, so as toreach almost the intermediate position between the magnetic case (i) 25and the magnetic case (ii) 28, is fixed to the slide member (i) 22.Further, as shown in FIG. 6, the holding member 17, at that time, so asto reach the axial position having a slight axial gap between therespective axial end faces and all the rollers, is connected to theslide member (i) 22 via the connection pin 21.

By use of the aforementioned constitution, in the first embodiment ofthe present invention, no power is supplied to both coils (i) 26 and(ii) 29, thus the axial position of the holding member 17 is kept at theintermediate position, and a wedge joint is formed by the direct actingrod 12 and the inclined surfaces in both directions, and to prevent frommoving in the axial direction by external force, the direct acting rod12 and the output shaft 31 fixed to it can be fixed.

FIG. 7 shows the state that power is supplied only to the coil (i) 26.At this time, magnetic attraction force is acted on the disk 23 in theleft direction and the slide member (i) 22 moves in the left directionuntil the disk 23 makes contact with the magnetic case (i) 25. At thistime, the axial position relationship between the holding member 17connected via the connection pin 21 and the rollers is as shown in FIG.8.

FIG. 8 shows the state that the holding member 17 moves in the leftdirection together with the slide member (i) 22, so that the rollers(ii) 14 and (iv) 16 on the right of which the axial end face of theholding member 17 is located make contact with the holding member 17 andare pressed out in the left direction. Namely, the rollers (ii) 14 and(iv) 16, even if pressed in the right direction by the pressing springs(ii) 18 and (i-iv) 19, are inhibited by the axial end face of theholding member 17, thereby cannot execute wedge joining. As a result,only wedge joining on the sections B-B (FIG. 2) and D-D (FIG. 4) shownin FIG. 7 can be realized. Further, the wedge joints on the sections B-Band D-D are wedge joints by the inclined surface in which the distancefrom the central axis (the direct acting rod or output shaft) increasesin the right direction of the shaft.

Here, the case that power supply to the coil 4 and interruption thereofare repeated will be considered. At time of power supply, a magneticcircuit is formed by the fixed iron core 2, frame 3, and movable ironcore 5 and the movable iron core 5 is attracted by the fixed iron core 2and is driven in the left direction by deforming the plate spring 6. Attime of interruption, the attraction force is eliminated and the movableiron core 5 is driven in the right direction by the restoration force ofthe plate spring 6. If the rigidity of the plate spring 6 is increasedsufficiently, it is possible to permit the movable iron core 5 toexecute an alternating motion driven right and left with a microamplitude by large force. Further, the state of the plate spring 6 shownin FIG. 7 indicates that it is at the neutral position of the left andright movement.

Next, the case that the vibration ring 7 fixed to the movable iron core5 executes the alternating motion in the state shown in FIG. 7 will beconsidered. When the spherical surface portion 7 b of the vibration ring7 is moving in the right direction (during movement), the inclinedsurface of the wedge joint in the cross sectional view B-B is aninclined surface in which the distance from the central axis decreasesin the left direction, so that the direct acting rod 12 cannot move inthe left direction to the vibration ring 7. On the other hand, theinclined surface of the wedge joint by the spherical surface portion libof the fixing ring 11 in the cross sectional view D-D is an inclinedsurface in which the distance from the central axis decreases in theright direction, so that the direct acting rod 12 is permitted to movein the right direction to the fixing ring 11. Namely, the direct actingrod 12 moves in the right direction together with the vibration ring 7.

On the other hand, when the spherical surface portion 7 b of thevibration ring 7 is moving in the left direction (during movement), thedirect acting rod 12 can move in the right direction to the vibrationring 7 and cannot move in the left direction to the fixing ring 11 (bythe wedge joint of the roller 15), so that the direct acting rod 12stands still together with the fixing ring 11 and only the vibrationring 7 returns in the left direction.

After all, when the holding member 17 is at the position shown in FIG.7, the direct acting rod 12 repeats an intermittent movement in theright direction (together with the rightward movement of the vibrationring 7) and even if one displacement is little, by accumulating it, canexecute a direct motion at a sufficiently large stroke in the rightdirection.

FIG. 9 shows the state that power is supplied only to the coil (ii) 29.At this time, magnetic attraction force is acted on the disk 23 in theright direction and the slide member (i) 22 with the disk 23 fixedovercomes the leftward force of the pressing spring (vi) 30 by therightward force which is the sum of the pressing force of the pressingspring (v) 24 and the concerned magnetic attraction force, thereby movesin the right direction. The slide member (i) 22 moves in the rightdirection until the disk 23 makes contact with the magnetic case (ii)28. At this time, the axial position relationship between the holdingmember 17 connected via the connection pin 21 and the rollers is asshown in FIG. 10.

FIG. 10 shows the state that the holding member 17 moves in the rightdirection together with the slide member (i) 22, so that the rollers (i)13 and (iii) 15 on the left of which the axial end face of the holdingmember 17 is located make contact with the holding member 17 and arepressed out in the right direction. Namely, the rollers (i) 13 and (iii)15, even if pressed in the left direction by the pressing springs (i-iv)19 and (iii) 20, are inhibited by the axial end face of the holdingmember 17, thereby cannot execute wedge joining. As a result, only wedgejoining on the sections C-C (FIG. 3) and E-E (FIG. 5) shown in FIG. 9can be realized. Further, the wedge joints on the sections C-C and E-Eare wedge joints by the inclined surface in which the distance from thecentral axis decreases in the right direction of the shaft.

Next, the case that the vibration ring 7 fixed to the movable iron core5 executes the alternating motion in the state shown in FIG. 9 byrepeating power supply to the coil 4 and interruption thereof will beconsidered. When the spherical surface portion 7 b of the vibration ring7 is moving in the right direction (during movement), the inclinedsurface of the wedge joint in the cross sectional view C-C is aninclined surface in which the distance from the central axis decreasesin the right direction, so that the direct acting rod 12 can move in theleft direction to the vibration ring 7. The inclined surface of thewedge joint by the spherical surface portion 11 b of the fixing ring 11in the cross sectional view E-E is an inclined surface in which thedistance from the central axis decreases in the right direction, so thatthe direct acting rod 12 cannot move in the right direction to thefixing ring 11. Namely, the direct acting rod 12 stands still togetherwith the fixing ring 11 and only the vibration ring 7 moves in the rightdirection.

On the other hand, when the spherical surface portion 7 b of thevibration ring 7 is moving in the left direction (during movement), thedirect acting rod 12 cannot move in the right direction to the vibrationring 7 and can move in the left direction to the fixing ring 11, so thatthe direct acting rod 12 moves in the left direction together with thevibration ring 7 by the wedge connection action of the roller 14.

After all, when the holding member 17 is at the position shown in FIG.9, the direct acting rod 12 repeats an intermittent movement in the leftdirection and even if one displacement is little, by accumulating it,can execute a direct motion at a sufficiently large stroke in the leftdirection.

In the structure of the first embodiment, the inclined surfaces of thewedge joining mechanism are all formed in the spherical surface portion7 b for executing only the alternating motion with a micro amplitude andthe spherical surface portion 11 b which is a fixed member, so that themass of the wedge joint inhibition mechanism, holding member 17 which isa drive apparatus thereof, and coils (i) 26 and (ii) 29 does not movetogether with the direct acting rod 12. Further, in the wedge joiningmechanism, the spherical surface portion 7 b which is an alternatingmotion member and the spherical surface portion 11 b fixed to thehousing are arranged on the outer peripheral side of the direct actingrod 12, and the diameter of the direct acting rod 12 becomes smaller,thus the mass is reduced. By the structure and arrangement thereof, theinertia resistance as a linear actuator is reduced. Further, the holdingmember 17 which is a wedge joint inhibition mechanism does not movetogether with the movement of the direct acting rod 12, and the coils(i) 26 and (ii) 29 are fixed, thus the lead wires for supplying power tothem will not be deformed in correspondence to the operation of thelinear actuator.

Further, the inclined surface in contact with the roller (i) 13 and theinclined surface in contact with the roller (ii) 14 are surfacesinclined mutually in the reverse directions (in the structure shown inFIG. 1, the inclined surface facing the roller 13 is inclined so as toseparate from the central axis in the right direction and the inclinedsurface facing the roller 14 is inclined so as to approach the centralaxis in the right direction) and the inclined surface in contact withthe roller (iii) 15 and the inclined surface in contact with the roller(iv) 16 are also surfaces inclined mutually in the reverse directions.The inclined surfaces have respectively two kinds of inclined surfaces,so that the inclined surface for forming a wedge joint can be selectedand switched, thus the direct acting rod 12 can be moved directly inboth directions by switching the direct acting direction.

Further, the wedge joint inhibition mechanism included in each wedgejoining mechanism is operated by the holding member 17 moving in thecommon direction such as the axial direction (the direct acting rod 12or output shaft 31), so that the holding member 17 can serve as aholding member of a plurality of wedge joint inhibition mechanisms.Actually, holding members of a plurality of wedge joint inhibitionmechanisms are united as a single holding member 17, and incorrespondence with it, regarding the slide member (i) 22, disk 23,pressing spring (v) 24, magnetic case (i) 25, coil (i) 26, slide member(ii) 27, magnetic case (ii) 28, coil (ii) 29, and pressing spring (vi)30 which compose the drive apparatus of the holding member 17, one setis enough, thus the number of components is reduced. In the firstembodiment, although there are 12 components provided, which is equal tothe total 12 of the rollers (i) 13, (ii) 14, (iii) 15, and (iv) 16 inwhich the wedge joint portion is a wedge member, regarding the holdingmember 17 of the wedge joint inhibition mechanism thereof and driveapparatus thereof, only one set each is enough.

Further, the rollers (i) 13, (ii) 14, (iii) 15, and (iv) 16 which arewedge members of the first embodiment are respectively a set of threerollers arranged in the circumferential direction, though each set isstructured so as to make contact with the common spherical surfacescontinuous in the circumferential direction such as the sphericalsurface portion 7 b or 11 b, so that there is no need to form inclinedsurface of the number of wedge members arranged in the circumferentialdirection.

Furthermore, the spherical surface portion 7 b serves as two kinds ofinclined surfaces inclined in the reverse directions such as theinclined surfaces corresponding to the set of the roller (i) 13 and theinclined surfaces corresponding to the set of the roller (ii) 14 and theinclined surfaces corresponding to six wedge members in total are formedby one spherical surface. The same may be said with the sphericalsurface portion 11 b corresponding to the set of the roller (iii) 15 andthe set of the roller (iv) 16.

Further, the contour of the outer peripheral surface of each of therollers (i) 13, (ii) 14, (iii) 15, and (iv) 16 which are wedge membersis formed at the curvature of the great circle of the spherical surfaceportion 7 b or lib, and the concave groove 12 a (refer to FIGS. 1 and 2)of the direct acting rod 12 in contact with each roller is also formedat the same curvature, so that at time of wedge joining, all thesections make line contact with each other. The so-called Hertz stressis relaxed.

The first embodiment is not a system of creating a direct motion via thefluid pressure, so that it is free of necessity of maintenance due toleakage of hydraulic oil and restrictions on the environment and by useof the aforementioned constitution, furthermore, the mass executing thedirect motion together with the output member is reduced, thus theeffect of high-speed response can be withdrawn more. Further, the numberof components and the processing man-hour are reduced and low cost canbe realized. Furthermore, the repetitive deformation of the lead wiresis avoided, and the Hertz stress of the inter-part contacting parts isrelaxed, thus the life span thereof can be lengthened. As a result, apracticable high-performance linear actuator can be provided.

Second Embodiment

The linear actuator relating to the second embodiment of the presentinvention will be explained below by referring to FIG. 11. FIG. 11 is across sectional view in the axial direction of the linear actuatorrelating to the second embodiment when the output shaft thereof isdriven in the left direction in the drawing.

In FIG. 11, in the second embodiment, the slide member (ii) 27, magneticcase (ii) 28, coil (ii) 29, and pressing spring (vi) 30 in the firstembodiment are not used and instead, a stopper 33 for controlling therightward movement of the slide member (i) 22 and disk 23 which areunited is incorporated. As a result, the holding member 17 moves in theleft or right direction depending on whether power is supplied to thecoil (i) 26 or not, enters the state shown in FIG. 8 or 10, and does notenter the state of the neutral position shown in FIG. 6. Namely, whenthe coil 26 is turned on, the holding member 17 enters the same state(the output shaft moves in the right direction) as that shown in FIG. 8and when the coil 26 is turned off, the holding member 17 enters thesame state (the output shaft moves in the left direction) as that shownin FIG. 10.

In the case of a one-way load instead of an alternating load thatexternal force acting on the output shaft 31 when the linear actuator isstopped is changed left and right, also in the second embodiment, eitherof the states shown in FIGS. 8 and 10 is selected and the output shaft31 can be prevented from moving by external force, so that theconstitution can be simplified. When driving left and right the outputshaft 31, similarly to the first embodiment, it is desirable to put theholding member 17 into the state shown in FIG. 8 or 10 and start thealternating drive apparatus 1.

Third Embodiment

The linear actuator relating to the third embodiment of the presentinvention will be explained in detail below by referring to FIGS. 12,13, and 14. FIG. 12 is a cross sectional view in the axial direction ofthe linear actuator relating to the third embodiment. FIG. 13 is adrawing of one of the two wedge joining mechanisms arranged in thecircumferential direction shown in FIG. 12 which is developed on aplane. FIG. 14 is a drawing of the other one of the two wedge joiningmechanisms arranged in the circumferential direction shown in FIG. 12which is developed on a plane.

In the third embodiment, an alternating drive apparatus 35 is composedof a rear case 36, a case 37, a coil 38, a magnetostrictor 39, and aconical spring 40 and gives an alternating motion in the axial directionto a vibration ring 41 which is an alternating motion member. Themagnetostrictor 39 is extended in the axial direction by a magneticfield generated by supplying power to the coil 38, drives the vibrationring 41 in the right direction, and when the power supply isinterrupted, is contracted to the original size due to disappearance ofthe magnetic field. At that time, the vibration ring 41 is driven in theleft direction by the conical spring 40. When repeating the power supplyand interruption for the coil 38 like this, the vibration ring 41 isdriven back and forth in the axial direction. According to the presentinvention, as an alternating drive apparatus, various forms can beapplied and it is possible to use the solenoid in the first embodiment,the magnetostrictor in the second embodiment, and furthermore, amagnetostrictor changing its dimensions due to impression of a voltagelike a pie zo-electric element.

Further, in the third embodiment, unlike the first and secondembodiments, a holding member (i) 49 of the first wedge joiningmechanism and a holding member (ii) 50 of the second wedge joiningmechanism are different members and magnetic disks (i) 51 and (ii) 52are fixed integrally with each of them. Further, the holding members arerespectively pressed by pressing springs (xi) 53 and (xii) 54 in theright direction and left direction in the drawing. Both holding memberscan move in the axial direction by the pressing springs until the disks(i) 51 and (ii) 52 make contact with a projection 42 a on the innerperipheral side of a housing 42. On the left and right of the disks (i)51 and (ii) 52, a magnetic case (iii) 59 and a magnetic case (iv) 60 arefixed respectively and in each magnetic case, a coil (iii) 61 and a coil(iv) 62 are fixed.

When power is supplied to the coil (iii) 61, it can attract the disk (i)51 in the left direction and when power is supplied to the coil (iv) 62,it can attract the disk (ii) 52 in the right direction. In FIG. 12,power is supplied only to the coil (iii) 61 among them, and the holdingmember (i) 49 is attracted in the left direction by the magnetic forcetogether with the disk (i) 51, and the holding member (ii) 50 is pressedin the left direction by a pressing spring (xii) 54 together with thedisk (ii) 52.

FIGS. 13 and 14 show drawings of the holding members (i) 49 and (ii) 50which are developed respectively on a plane. Among rollers (v) 45,rollers (vi) 46, rollers (vii) 47, and rollers (viii) 48 which arearranged respectively in three pieces on circumferences at differentaxial positions, the rollers (vi) 46 and (viii) 48 on the right of whichthe axial end faces of the holding members 49 and 50 are adjacent arepressed out by the leftward movement of the holding members (i) 49 and(ii) 50 and cannot be wedge-joined. In the first and second wedgejoining mechanisms, the state that only the residual rollers (v) 45 and(vii) 47 can be wedge-joined, in the first embodiment, is the stateshown in FIG. 7 or 8 and by the principle and operation explained in thefirst embodiment, the direct acting rod 44 and output shaft 31 aredriven in the right direction in the drawing by the alternating driveapparatus 35. When intending to drive them in the left direction, it isdesirable to supply power inversely only to the coil (iv) 62.

Further, the holding member (i) 49 of the third embodiment is a commonholding member in which a holding member for inhibiting wedge-joiningincluding the roller (v) 45 and a holding member for inhibitingwedge-joining including the roller (vi) 46 are united and the holdingmember (ii) 50 is a common holding member in which a holding member forinhibiting wedge-joining including the roller (vii) 47 and a holdingmember for inhibiting wedge-joining including the roller (viii) 48 areunited. In this connection, the first embodiment unites furthermorethese common holding members.

In the third embodiment, by uniting even if partially, the number ofholding members and the number of components for driving them can bereduced to a certain extent. Further, as a peculiar effect of the thirdembodiment, by supplying no power to both coils (iii) 61 and (iv) 62 orsupplying power to both of them, a state that the wedge joint by theinclined surfaces in the reverse directions functions (when the coils 61and 62 are supplied or not supplied with power, the direct acting rod 44cannot move in any direction) is realized and even if the mechanism forholding the holding member at the neutral position (the stop positionshown in FIG. 1) as described in the first embodiment is not provided,the output shaft 31 can be fixed for external force changing due toalternation when the linear actuator is stopped.

As explained above, the main characteristic of the linear actuatorrelating to the embodiments of the present invention is a one created tosolve the following problem of the prior art and produces a peculiareffect which cannot be obtained by the prior art. Namely, in theconventional linear actuator for accumulating the one-way motion of thealternating motion by the alternating drive source and creating a directmotion, a problem arises that the mass of the portion for executing thedirect motion is increased, and the inertia resistance is increased,thus improvement of the response speed is inhibited and furthermore, aproblem of durability arises that the drive apparatus for the functionof switching the direct acting direction moves, so that the power supplyroute such as the lead wire is deformed frequently. Further, the priorart has many wedge joining mechanisms and in correspondence to them,many wedge joint inhibition mechanisms and drive apparatus thereof arerequired and a problem arises that the number of components and theprocessing man-hour of the inclined surfaces of the wedge joiningmechanisms are increased, thus an increase in cost is caused.

Therefore, in the embodiments of the present invention, in the linearactuator for accumulating the one-way motion of the alternating motionby the alternating drive source and creating a direct motion, to realizehigh-speed response, decrease in cost, and long life span by reductionin the mass of direct acting portions, reduction in the numbers ofcomponents and processing steps, and reduction in the contact surfacepressure is assumed as a main object of problem solution. And, as aconcrete measure for solving the problems, a constitution that theinclined surfaces of the wedge joining mechanisms are not formed on thedirect acting member side is used, and the mass of the wedge jointinhibition mechanisms and drive apparatuses thereof is not added to themass of the portion for executing the direct motion, and furthermore, inall the wedge joining mechanisms, the direct acting members are arrangedon the inner peripheral side, and the mass thereof is reduced, thus theinertia resistance is reduced. Further, the drive apparatuses for thewedge joint inhibition mechanisms are fixed, thus the lead wires are notdeformed.

Furthermore, a constitution that the holding members which arecomponents of the wedge joint inhibition mechanisms included in eachwedge joining mechanism can be united is used, thus the number ofcomponents is reduced and in correspondence with it, the number of driveapparatuses thereof is reduced. Further, a plurality of inclinedsurfaces necessary for each wedge joining mechanism are formed as a partof the common spherical surface, thus the processing man-hour isreduced. In correspondence with that the inclined surfaces are formed asa spherical surface, the wedge members in contact with it are formed ina shape of making line contact with the spherical surface andfurthermore, the contact portions with the wedge members of non-inclinedmembers are formed in a shape for making line contact. Therefore, theinclined surfaces can be avoided from reduction in the fatigue life dueto large stress generated by point contact.

The action and effect of the linear actuator relating to the embodimentsof the present invention will be explained more below. Namely, in themechanism for generating a direct motion of the direct acting membersfrom the alternating motion of the alternating motion members using thewedge joining mechanism, the inclined surfaces of the wedge joiningmechanism are never formed on the direct acting members but are formedon the fixing members fixed to the housing member and the alternatingmotion members for executing only the alternating motion with a microamplitude. In consideration of the case that the wedge joint inhibitionmechanism for inhibiting wedge joining of the wedge joining mechanism ismounted, the wedge joint inhibition mechanism must be fixed for theinclined surface surely existing on the wedge joint portion instead ofthe non-inclined surface moving in the axial direction for the wedgejoint portion.

In this embodiment, in the direct acting members having no inclinedsurfaces formed, there is no need to mount the drive apparatuses such asthe wedge joint inhibition mechanism and solenoid for driving it and themass of the portion for executing the direct motion as output can beprevented from increasing. Therefore, the inertia resistance whenfunctioning as a linear actuator is reduced, thus a high-speed responseis enabled. Further, the drive apparatuses of the wedge joint inhibitionmechanism can be mounted on the fixing members, so that when supplyingpower to them via lead wires, the stress due to deformation incorrespondence with the operation of the actuator will not actrepeatedly and the durability thereof can be ensured.

Further, according to this embodiment, the direct acting members whichare output members are arranged in the neighborhood of the central axisin the overall constitution of the actuator, thereby can be storedwithin a range at a small diameter from the central axis. Therefore, themass of the direct acting members themselves can be made smaller, sothat the inertia resistance when functioning as a linear actuator isreduced, thus a higher-speed response is enabled.

Further, according to this embodiment, the inclined surface for forminga wedge joint can be selected and switched from the two kinds of forwardand backward inclined surfaces, so that the direct acting directioninfluenced by the inclination direction of the inclined surface of thewedge joint is switched, thus the direct acting member can be acteddirectly in both directions. Furthermore, each holding member for theoperation of each wedge joint inhibition mechanism is operated by movingin the common axial direction, so that the holding members can beunited. Furthermore, the holding member for inhibiting contact of theforward inclined surface with the wedge member and the holding memberfor inhibiting contact of the backward inclined surface with the wedgemember are united, thus the number of components is reduced, andfurthermore, they can be driven by the common holding member drivemechanism, so that the cost of the linear actuator can be decreased.

Further, according to this embodiment, one holding member of the linearactuator and one holding member drive mechanism thereof are enough, sothat the cost of the linear actuator can be decreased more. Furthermore,there is no need to form inclined surfaces for wedge joining for aplurality of wedge members arranged in the circumferential direction andone spherical surface continuous on the overall circumference is justformed. Furthermore, the spherical surface itself is formed in a rotatorshape and an easily processed shape, so that the cost of the linearactuator can be decreased.

Further, according to this embodiment, the forward inclined surface andbackward inclined surface do not need to be formed as separate inclinedsurfaces and can be formed by a common inner peripheral sphericalsurface, so that the cost of the linear actuator can be decreased more.Furthermore, to decrease the cost, even if the inclined surfaces areformed by a spherical surface continuous in the circumferentialdirection, the contacting part of the wedge member with the inclinedsurface and the contacting part of the wedge member with thenon-inclined surface can be formed as a line contact instead of a pointcontact and the material fatigue progressed by the Hertz stressgenerated at the contacting part is relaxed and the flaking life can belengthened.

Fourth Embodiment

Hereinafter, the linear actuator relating to the fourth embodiment willbe explained by referring to FIGS. 15 to 19. FIG. 15 is a crosssectional view in the axial direction of the linear actuator, which is adrawing showing the section A-A shown in FIGS. 16 and 17. FIG. 16 is atransverse cross sectional view of the linear actuator to show thesections B-B and E-E shown in FIG. 15 and FIG. 17 is a transverse crosssectional view of the linear actuator to show the sections C-C and D-Dshown in FIG. 15. FIG. 18 is a drawing to show a principle of drivingthe output shaft when the distance in the axial direction between thetwo joint members is increased in the linear actuator shown in FIG. 15and FIG. 19 is a drawing to show a principle of driving the output shaftwhen the distance in the axial direction between the two joint membersis decreased in the linear actuator shown in FIG. 15.

In FIG. 15, an alternating drive apparatus 101 is composed of amagnetostrictor 102 and a coil 103. On both sides of the magnetostrictor102 in the axial direction, two joint members 104 are closely adheredrespectively via a spring holder 105. Outside each of the joint members104, the spring holder 105 is also adhered closely and furthermore,outside it, a conical spring 106 which is a pressing member in the axialdirection is arranged. These components are adhered closely to eachother in the axial direction and are held and incorporated in the axialdirection in a housing 109 composed of a casing 107 and two side ends108. The two joint members 104 equivalent to a first joint member and asecond joint member can slide respectively on the adhered surfaces withthe adjacent components. Therefore, they are not fixed in the radialdirection. Further, the two joint members 104 can execute respectivelythe alternating motion in the axial direction by expansion andcontraction of the magnetostrictor 102 of the alternating driveapparatus 101 and serve as a first alternating motion member and asecond alternating motion member.

In the two side ends 108, shaft support portions 108 a having an innerperipheral cylindrical surface are formed and here, a direct actingmember 110 having the sectional shape shown in FIGS. 16 and 17 isrestricted in the radial direction and is supported so as to move in theaxial direction. The direct acting member 110 has no article forblocking the axial direction, thereby moves through the two side ends108.

In the joint members 104 serving as the first alternating motion memberand second alternating motion member, an inner peripheral sphericalsurface portion 104 a is formed and in the direct acting member 110, aconcave groove 110 a is formed. And, between the two surfaces, a roller111 which is a wedge member for wedge joining is arranged. The wedgejoint is formed by a surface inclined in the axial direction (inclinedsurface), a surface not inclined in the axial direction (non-inclinedsurface), and a wedge member, though the non-inclined surfaces in thisembodiment are all fixed to the direct acting member 110 as a concavegroove 110 a and the inclined surfaces are fixed to the joint members104 serving as the first alternating motion member and secondalternating motion member as an inner peripheral spherical surfaceportion 104 a.

The radius of curvature of the section perpendicular to the axis (FIGS.16, 17) of the concave groove 110 a is equal to the radius of the greatcircle of the inner peripheral spherical surface portion 104 a and theroller 111, since the contour of the outer peripheral part thereof isformed by the concerned radius, can make contact with any wedge-joiningsurface in a line contact form. The roller 111 plays a roll that at eachof the sections B-B, C-C, D-D, and E-E shown in FIG. 15, three piecesare incorporated in the circumferential direction and guide portions 112a of a holding member 112 shown in FIGS. 16 and 17 arrange the threerollers 111 at predetermined intervals in the circumferential direction.In the holding member 112, notches for inserting the rollers 111 fromone end of the cylindrical member in the axial direction are formed atthree locations and between the notches, notches for inserting therollers 111 at different three locations from the other end thereof inthe axial direction are formed. As a result, two adjacent guide portions112 a at the six locations of each of the holding members 112 areconnected by connection portions 112 b shown in FIG. 15 and are unitedas a whole.

To the connection portions 112 b arranged outside each of the holdingmembers 112, disks 115 composed of a magnetic substance are connectedvia a connection pin 114. Opposite to the inner side wall of each of thedisks 115, coil portion assemblies 116 composed of a coil and a U-shapedmagnetic substance are fixed. The left and right disks 115 are pressedexternally by springs 117 incorporated between the side ends 108 andthemselves and when power is supplied to the coil portion assemblies116, are attracted inside by the magnetic attraction force. Themovement, when outward, is restricted due to contact of the side ends108 with the connection pins 114 and when inward, is restricted due tocontact of the disks 115 with the coil portion assemblies 116.

Between the spring holder 105 and each of the rollers 111, a pressingspring 113 is incorporated and presses each of the rollers 111 towardthe connection portion 112 b of the holding member 112. If each of therollers 111 is held between the inner peripheral spherical surfaceportion 104 a and the concave groove 110 a by the pressing force beforeit makes contact with the connection portion 112 b, wedge joining isrealized and if it makes earlier contact with the connection portion 112b, the wedge joining is inhibited. Further, depending on the dimensionalrelationship between the portions, at time of wedge joining, each of therollers 111 and the inner peripheral spherical surface portion 104 amake surely contact with each other at a position shifted in the axialdirection from the spherical center of the inner peripheral sphericalsurface portion 104 a such as the sections B-B, C-C, D-D, and E-E.Therefore, the tangential direction at the contact point shown in FIG.15 is inclined surely with the axial direction and the inner peripheralspherical surface portion 104 a becomes an inclined surface. On theother hand, the concave groove 110 a is always parallel with the axialdirection and becomes a non-inclined surface.

In FIG. 15, the coil portion assembly 116 on the right is not suppliedwith power and the holding members 112 on the right move respectivelyrightward by the springs 117. On the other hand, the coil portionassembly 116 on the left is supplied with power and the holding members112 on the left, since the disks 115 are attracted by the coil portionassembly 116, move also rightward. As a result, the rollers 111 at thesections B-B and D-D are pressed out by the connection portions 112 band are put into the state that wedge joining is inhibited, and therollers 111 at the sections C-C and E-E move away from the connectionportions 112 b and are put into the state that wedge joining can berealized surely.

Next, the principle that the alternating motion generated by thealternating drive apparatus 101 is converted to a one-way direct motionwill be explained by referring to FIGS. 18 and 19. In FIGS. 18 and 19,only the parts directly relating to the conversion principle from thealternating motion to the direct motion are shown.

Further, the rollers 111 at the sections B-B and D-D that the wedgejoining is inhibited in FIG. 15 are omitted and only the rollers 111 atthe sections C-C and E-E that the wedge joining is enabled are shown.Further, as shown in FIGS. 15 to 17, the roller 111 at the section C-Cand the roller 111 at the section E-E are arranged at shifted positionsin the circumferential direction, and the rollers 111 are not originallyillustrated simultaneously on the sections shown in FIGS. 18 and 19,though for explanation of the principle of realization of direct action,they are illustrated on the same section for convenience.

FIG. 18 shows the state that by power supply to the coil 103 of thealternating drive apparatus 101, the shaft length of the magnetostrictor102 is extended and the joint members 104 respectively move externally.At this time, in the inner peripheral spherical surface portion 104 a onthe right, roller 111, and concave groove 110 a, no wedge joint isformed in the motion direction of the joint member 104 to the directacting member 110, though in the inner peripheral spherical surfaceportion 104 a on the left, roller 111, and concave groove 110 a, a wedgejoint is formed, thus the direct acting member 110 is driven in the leftdirection in the drawing. FIG. 19 shows the state that the power supplyto the coil 103 of the alternating drive apparatus 101 is interrupted,and the shaft length of the magnetostrictor 102 is contracted, and thejoint members 104 respectively move internally by the conical springs106. At this time, in the inner peripheral spherical surface portion 104a on the left, roller 111, and concave groove 110 a, no wedge joint isformed in the motion direction of the joint member 104 to the directacting member 110, though in the inner peripheral spherical surfaceportion 104 a on the right, roller 111, and concave groove 110 a, awedge joint is formed, thus the direct acting member 110 is driven alsoin the left direction in the drawing. After all, even when the shaftlength of the magnetostrictor 102 is extended or contracted, the directacting member 110 and output shaft 118 fixed to it are driven in theleft direction and can execute a comparatively smooth direct motion.

Unlike FIG. 15, the case that the coil portion assembly 116 on the rightis supplied with power, and the holding members 112 on the right aremoved leftward by the magnetic attraction force of the disk 115 and thecoil portion assembly 116, and the coil portion assembly 116 on the leftis not supplied with power, and the holding members 112 on the left arealso moved leftward by the springs 117 will be considered. In this case,the rollers 111 at the sections C-C and E-E are pressed out by theconnection portions 112 b and are put into the state that wedge joiningis inhibited, and the rollers 111 at the sections B-B and D-D move awayfrom the connection portions 112 b and are put into the state that wedgejoining can be realized surely. The parts directly relating to theconversion principle from the alternating motion to the direct motion atthat time, in FIGS. 18 and 19, are put into the state that the partsother than the output shaft 118 are inverted left and right. At thistime, when the shaft length of the magnetostrictor 102 is extended orcontracted, the direct acting member 110 and the output shaft 118 fixedto it are driven in the right direction and it can be analogized easilythat they execute also a comparatively smooth direct motion.

As a result of this, a linear actuator capable of permitting the directacting member 110 and output shaft 118 to execute the direct motion inthe longitudinal direction can be structured.

Fifth Embodiment

Hereinafter, the linear actuator relating to the fifth embodiment willbe explained by referring to FIG. 20. FIG. 20 is a cross sectional viewin the axial direction of the linear actuator relating to the fifthembodiment.

In this embodiment, an alternating drive apparatus 119 is composed of acoil 120 and two movable iron cores 121. The two movable iron cores 121,when at least the coil 120 is not supplied with power, are arranged inthe axial direction opposite to each other in the state that there is agap at the central part. On the inner peripheral part of each of themovable iron cores 121, a joint member 122 and spring holders 123 onboth sides thereof are arranged and are restricted on movement outsidethe axial direction to each of the movable iron cores 121 by an E ring124 and a washer 125. This movement restriction section is always keptin the joined state by a spacer 12 and a conical spring (i) 127 whichare arranged at the central part. The left and right movable iron cores121 are additionally held and incorporated between a housing (i) 129 anda housing (ii) 130, which are made of a magnetic substance, in the axialdirection via a conical spring (ii) 128. The gap aforementioned is setat a predetermined gap by adjusting the spring force acted by theconical springs (i) 127 and (ii) 128.

When the coil 120 is supplied with power, the two movable iron cores 121attract each other, slide to the housing (i) 129 or (ii) 130, and movetoward the center to reduce the gap. At that time, the movable ironcores permit the left and right joint members 122 to move together toreduce the distance between the joint members 122 in the axialdirection. When the power supply to the coil 120 is interrupted, thejoint members 122 extend the axial distance thereof by the spring forceof the conical spring (i) 127 and simultaneously recover the gap betweenthe two movable iron cores 121. Namely, the fifth embodiment indicatesthat the axial distance between the left and right joint members 122 canbe extended or contracted by the magnetic force. Further, each of thejoint members 122 can slide on the joined surfaces with the neighboringcomponents thereof, so that it is not fixed in the radial direction.

The principle and constitution of creating a direct motion in thelongitudinal direction from the two joint members 122 the axial distanceof which extends or contracts are the same as those of the fourthembodiment. However, coil portion assemblies 131 and disks 132 of thefifth embodiment are incorporated in the opposite left and rightposition relationship of that of the coil portion assemblies 116 anddisks 115 of the fourth embodiment, so that the relationship between thedirection in which a direct acting member 133 and an output shaft 134are to be moved directly and the coil portion assembly 131 to besupplied with power among the two coil portion assemblies 131 is reverseto the relationship explained in the fourth embodiment.

As explained above, according to this embodiment, (1) the direct actingmember 133 is supported in the radial direction by the shaft supportportions 129 a, 130 a provided in the housing member, so that the radialload and moment acting on the direct acting member 133 from the outsidecan be supported by the shaft support portions 129 a, 130 a. Further,the first and second joint members 122 are structured so as not to befixed in the radial direction, so that they will not support the radialload and moment acting on the direct acting member 133 from the outside.Namely, external force can be prevented from acting on the first andsecond wedge joining mechanisms incorporated between the first andsecond joining members 122 and the direct acting member 133. Further,when the first wedge joining mechanism or second wedge joining mechanismis put into the wedge joining state and a radial load is generated by aresultant force of the acting force of each wedge joint portion in eachwedge joining mechanism, each joint member 122 moves in the radialdirection and the radial load aforementioned is eliminated. Namely, theload due to wedge joining can be prevented from acting between eachjoint member 122 and the direct acting member 133. As a result of this,the credibility of the wedge joining mechanisms and shaft supportportion can be enhanced.

(2) Both the first and second joint members 122 execute the alternatingmotion. Therefore, in all the cases that the axial distance between themis increased by the alternating drive apparatus 119 and it is decreased,either of the joint members 122 moves in the direction for driving thedirect acting member 133. By use of it, it is possible to decrease thetime zone that the direct acting member 133 is stopped and realize asmoother direct motion using the alternating drive apparatus 119.Further, the joint members 122 moving back and forth can cancel mutuallya part of the inertia force, so that low vibration can be realized.Further, the components can be standardized easily such that the firstand second joint members 122 are formed as a same component, thus thecost can be decreased.

(3) The alternating drive apparatus 119, first alternating motionmember, and second alternating motion member are structured so as to beheld between the housing members 129, 130 in the axial direction via aspring element. Therefore, an assembly step of fixing each component isnot necessary. Therefore, the cost can be decreased.

(4) The alternating drive apparatus 199 is arranged on the outerperipheral part of the direct acting member 133, thereby will not blockthe direct acting direction of the direct acting member 133. Therefore,there is no need to reserve a space corresponding to the stroke of thedirect acting member 133 for avoiding interference between thealternating drive apparatus 119 and the direct acting member 133 betweenthe two. Therefore, the actuator can be made smaller. Further, only byincreasing the length of the direct acting member 133, the stroke of thelinear actuator can be enlarged.

(5) The direct acting members 133 pass through the housing members 129,130 on both sides in the axial direction and are supported in the radialdirection by the two shaft support portions 129 a, 130 a provided ateach through portion thereof. Namely, each direct acting member 133 isshaft-supported at the two locations at a comparatively long span, sothat the support load when moment is acted externally is reduced and thecredibility is improved. Further, the direct acting members 133 passthrough the housing members 129, 130, so that there is no need toreserve internally a space corresponding to the stroke of the directacting members 133 and the linear actuator can be made smaller.

(6) The non-inclined surface of the first wedge joining mechanism andthe non-inclined surface of the second wedge joining mechanism are fixedto the direct acting members 133 and the inclined surface of the firstwedge joining mechanism and the inclined surface of the second wedgejoining mechanism are fixed respectively to the first alternating motionmember and second alternating motion member. Here, in consideration ofthe case that to inhibit wedge joining of the wedge joining mechanism,the wedge joint inhibition mechanism is mounted, the concerned wedgejoint inhibition mechanism must be fixed to the inclined surfaceexisting surely in the wedge joint portion instead of the non-inclinedsurface for moving for the wedge joint portion in the axial direction.Namely, that the inclined surfaces of the wedge joining mechanism arenot formed in the direct acting member 133 but formed in the firstalternating motion member and second alternating motion member whichexecute an alternating motion with a micro amplitude is advantageousfrom this viewpoint.

Further, in the direct acting member 133 having no formed inclinedsurface, there is no need to mount drive apparatuses such as a wedgejoint inhibition mechanism and a solenoid for driving it. Therefore, themass of the portion for executing the direct motion as output can beprevented from increasing. Therefore, the inertia resistance whenfunctioning as a linear actuator is reduced, thus a high-speed responseis enabled. Further, the drive apparatuses of the wedge joint inhibitionmechanism can be mounted on the fixing members, so that when supplyingpower to them via lead wires, the stress due to deformation incorrespondence with the operation of the actuator will not actrepeatedly and the durability thereof can be ensured.

(7) The first and second wedge joining mechanisms have respectively twokinds of inclined surfaces such as a forward inclined surface at adistance from the central axis decreasing in one axial direction and abackward inclined surface at a distance increasing, permit the wedgejoint inhibition mechanisms on the respective inclined surfaces tooperate selectively, and include a wedge joining direction convertingfunction for selecting the inclined surface for forming a wedge jointtogether with the non-inclined surfaces and wedge members from the twokinds of inclined surfaces. Namely, the wedge joining mechanisms canselect and switch the inclined surface for forming a wedge joint fromthe two kinds of forward and backward inclined surfaces. Therefore, thedirect acting direction controlled by the inclination direction of theinclined surface of the wedge joint is switched, thus the direct actingmember 133 can be moved directly in both directions.

Further, each holding member for operating each wedge joint inhibitionmechanism operates by moving in the common axial direction, so that theholding members can be united.

(8) At least one of the first and second wedge joining mechanisms has acommon holding member in which the holding member for inhibiting thecontact of the forward inclined surface with the wedge member and theholding member for inhibiting the contact of the backward inclinedsurface with the wedge member are united. As mentioned above, theholding member for inhibiting the contact of the forward inclinedsurface with the wedge member and the holding member for inhibiting thecontact of the backward inclined surface with the wedge member areunited, thus the number of components is reduced and furthermore, theycan be driven by the common holding member drive mechanism. Therefore,the cost of the linear actuator can be decreased.

(9) At least one of the first and second wedge joining mechanisms has aplurality of wedge members arranged in the circumferential direction andthe inclined surfaces in contact with them are formed by a common innerperipheral spherical surface. Therefore, for all the plurality of wedgemembers arranged in the circumferential direction, there is no need toform inclined surfaces for wedge joining and it is acceptable to formonly one spherical surface having an overall continuous circumference.Furthermore, the spherical surface itself is in a rotator shape and inan easily-processed shape, so that the cost of the linear actuator canbe decreased.

(10) Thy forward inclined surface and backward inclined surface of atleast one of the first and second wedge joining mechanisms are formed bya common inner peripheral spherical surface. Therefore, there is no needto form the forward inclined surface and backward inclined surface asseparate inclined surfaces and can be formed by a common innerperipheral spherical surface. Therefore, the cost of the linear actuatorcan be decreased.

(11) The wedge member in contact with the inclined surface formed by apart of the inner peripheral spherical surface is generally a rotatorhaving a part of the great circle of the concerned spherical surface asa contour shape and the non-inclined surface of the direct acting member133 in contact with the concerned wedge member is formed by a concavegroove 133 a having a part of the great circle aforementioned on thecontour of the section perpendicular to the axis. Namely, to decreasethe cost, even if the inclined surfaces are formed by a sphericalsurface continuous in the circumferential direction, the contacting partof the wedge member with the inclined surface and the contacting part ofthe wedge member with the non-inclined surface can be formed as a linecontact instead of a point contact and the material fatigue progressedby the Hertz stress generated at the contacting part is relaxed and theflaking life can be lengthened.

(12) The linear actuator includes an alternating drive apparatus 119 forgenerating drive force back and forth in the axial direction, a firstalternating motion member and a second alternating motion member forexecuting an alternating motion by the alternating drive apparatus 119,a housing member 129, 130 which is a fixing member, a direct actingmember 133 for executing a direct motion back and forth in the axialdirection, a first wedge joining mechanism incorporated between thefirst alternating motion member and the direct acting member 133 forpermitting an axial relative displacement in one axial direction betweenthe two and inhibiting an axial relative displacement in the other axialdirection, and a second wedge joining mechanism incorporated between thesecond alternating motion member and the direct acting member 133 forpermitting an axial relative displacement in one axial direction betweenthe two and inhibiting an axial relative displacement in the other axialdirection.

Therefore, the direct acting member 133 can execute a smoother directmotion using the alternating drive apparatus 119 independently of theshaft support structure of the direct acting member 133. Further, thejoint members moving back and forth can cancel mutually a part of theinertia force, so that low vibration can be realized.

(13) The linear actuator can drive the variable operating valvemechanism. In this case, for the automatic transmission controlled bythe concerned movable valve or the variable operating valve mechanism,high credibility, low vibration, low cost, and long life span can berealized.

As explained above, according to this embodiment, each load supportportion is prevented from action of a surplus load, thus highcredibility can be realized. Further, low vibration due to mutual cancelof inertia force, low cost due to standardization of components andreduction in the processing man-hour and assembly man-hour, andminiaturization and long stroke due to avoidance of interference ofcomponents can be realized. Further, the mass for executing the directmotion together with the direct acting member 133 is reduced to realizehigh response, and the Hertz stress (contact stress) of theinter-component contacting part is relaxed, thus the life span can belengthened. Therefore, a practicable high-performance linear actuatorcan be obtained.

1. A linear actuator comprising: first and second joint members, ahousing member for storing the first and second joint members, a driveapparatus for driving the first and second joint members in a mutuallyapproaching direction thereof and in a separating direction thereof inthe housing member, a direct acting member joined to the first andsecond joint members for executing a linear motion in an axialdirection, a first wedge joining mechanism incorporated between thefirst joint member and the direct acting member for permitting arelative displacement in one axial direction between the first jointmember and the direct acting member and inhibiting a relativedisplacement in the other axial direction between the first joint memberand the direct acting member, and a second wedge joining mechanismincorporated between the second joint member and the direct actingmember for permitting a relative displacement in one axial directionbetween the second joint member and the direct acting member andinhibiting a relative displacement in the other axial direction betweenthe second joint member and the direct acting member, wherein: the firstwedge joining mechanism and the second wedge joining mechanism includean inclined surface at a distance from a central axis changing in theaxial direction, a non-inclined surface at a constant distance from thecentral axis, and a wedge member arranged between them, and the directacting member is supported in a radial direction by a shaft supportsection provided in the housing member.
 2. The linear actuator accordingto claim 1, wherein the first and second joint members are restricted ona radial position by the direct acting member.
 3. The linear actuatoraccording to claim 1, further comprising a wedge joint inhibitionmechanism for inhibiting wedge joining by the wedge member.
 4. Thelinear actuator according to claim 1, wherein the drive apparatusincludes a pair of movable iron cores sliding in the axial direction, aspring arranged between the movable iron cores for driving the movableiron cores in a direction for separating them from each other, and amagnetic coil for driving the movable iron cores in a direction forbringing the movable iron cores close to each other, wherein themagnetic coil is supplied with power to generate drive force forextending and contracting the paired movable iron cores in the axialdirection.
 5. The linear actuator according to claim 1, wherein thefirst and second joint members make contact respectively with twosurfaces of the drive apparatus orthogonal to the axial direction andsprings are arranged additionally outside the first and second jointmembers and are held by the housing member in the axial direction. 6.The linear actuator according to claim 1, wherein the first and secondjoint members are arranged on an outer peripheral part of the directacting member.
 7. The linear actuator according to claim 1, wherein atleast one of the first and second wedge joining mechanisms has aplurality of wedge members arranged in a circumferential direction andthe inclined surfaces in contact with the wedge members are formed by acommon inner peripheral spherical surface.
 8. The linear actuatoraccording to claim 7, wherein a forward inclined surface and a backwardinclined surface of at least one of the first and the second wedgejoining mechanisms are formed by a common inner peripheral sphericalsurface.
 9. The linear actuator according to claim 7, wherein the wedgemember in contact with the inclined surface formed by a part of theinner peripheral spherical surface is a rotator having a contour shapecomposed of a part of a great circle of the spherical surface and thenon-inclined surface of the direct acting member in contact with thewedge member is a concave groove having a contour of a right-angledsection thereof composed of a part of the great circle.
 10. The linearactuator according to claim 8, wherein the wedge member in contact withthe inclined surface formed by a part of the inner peripheral sphericalsurface is a rotator having a contour shape composed of a part of agreat circle of the spherical surface and the non-inclined surface ofthe direct acting member in contact with the wedge member is a concavegroove having a contour of a right-angled section thereof composed of apart of the great circle.